Holmium(III) chloride
# Holmium(III) chloride

Holmium(III) chloride is the inorganic compound with the formula $HoCl_3.$ It is a common salt but is mainly used in research. It can be used to produce pure holmium. It exhibits the same color-changing behavior seen in holmium oxide, being a yellow in natural lighting and a bright pink color in fluorescent lighting.

## Preparation

The most commonly used method to obtain holmium(III) chloride involves heating a mixture of holmium(III) oxide and ammonium chloride at 200-250 °C:

    $Ho_2O_3$ + 6 $NH_4Cl$ → 2 $HoCl_3$ + 6 $NH_3$ + 2 $H_2O$

The hexahydrate of holmium(III) chloride can be obtained by reaction between holmium and hydrochloric acid:

    2 Ho + 6 HCl → 2 $HoCl_3$ + 3 $H_2$

It can also be prepared by the direct reaction between holmium and chlorine:

    2 Ho + 3 $Cl_2$ → 2 $HoCl_3$

## Properties

Holmium(III) chloride and its hexahydrate are light yellow solids in daylight that are soluble in water. The hexahydrate starts to release water of crystallization at 64 °C. Holmium(III) chloride has a monoclinic crystal structure analogous to that of aluminum(III) chloride. In the solid state it has the $YCl_3$ layer structure.

